This invention relates to glide heads used to detect defects on the surface of magnetic or magnetic-optical memory disks such as those used in hard disk drives.
A computer hard disk drive comprises a memory disk mounted on a spindle which is driven by a motor to rotate the disk at high speed. A read/write head, kept in close proximity to the surface of the rotating disk, reads or writes data on the disk, which may be a magnetic or magneto-optic disk. The read/write head is separated from the surface of the disk by an air bearing created by the high speed rotation of the disk. The read/write head flies on this air bearing, e.g., at a height of approximately 1xcexcxe2x80x3 (one microinch) above the surface of the disk. The density of the information written on the disk is increased as the read/write head flies closer to the surface of the disk. Thus, it is desirable for the read/write head to fly as close as possible to the surface of the magnetic disk.
Typical memory disks comprise, e.g., an aluminum substrate that is plated with a hard material, such as a nickel phosphorus alloy. The nickel phosphorus is then textured or roughened. An underlayer, a magnetic alloy or magnetic-optical material, and a protective overcoat are then deposited on the nickel phosphorus, e.g., by sputtering. The disk manufacturing process leaves the surface of the disk in a slightly roughened condition. Although magnetic disks are typically textured to have a specified roughness, there has been a trend in the industry to make magnetic disks smoother and smoother. Presently, some magnetic disks are specified to have a roughness less than or equal to about 30 xc3x85 (3 nm).
The precision with which the read/write head flies over the magnetic disk requires that care is taken during manufacturing to assure that there are no protrusions or asperities on the disk surface that may interfere with the read/write head. A protrusion on the surface of the disk that contacts the read/write head during use may damage the head or the disk.
Accordingly, tests are performed on finished disks using media certifiers to determine if there are any asperities, voids, or contamination that might interfere with the read/write head. Accurate testing of disks for such defects assures that the disk manufacturer does not unnecessarily reject good quality disks or pass on poor quality disks that may later fail.
Glide heads are used in conjunction with media certifiers to detect the asperities and depressions. Glide heads are similar to read/write heads in that it includes a slider which rests or flys on the air bearing formed by the rotating disk. A transducer is mounted on the glide head. If the glide head collides with a defect on the rotating disk, e.g. an asperity, the mechanical shock from the collision with the defect will cause the transducer to create an electrical signal, which is received by a circuit in the media certifier via wires. This circuit identifies signals caused by collisions between glide head and defects. The larger the defect, the larger the electrical signal created by the transducer and sensed by the circuit within the media certifier.
In general, glide heads, like read/write heads, have continued to decrease in size over time. For example, glide heads, and sliders in general, decreased in size to 70% sliders (the percentage describes the size of the glide head relative to the original slider size, which is known as 100%) to the now industry standard 50% glide heads. An original 100% slider has a length of 0.16 inches, a width of 0.125 inches, and a height of 0.034 inches. The suspension arms to which glide heads are mounted, however, have not had a corresponding reduction in size.
FIGS. 1 and 2 show bottom and front views, respectively, of a conventional 50% glide head 10. Glide head 10 includes a slider 12 that has two rails 14 and 16 with respective tapered leading ends 15 and 17. Glide head 10 also includes a wing 18 that serves as an extension to the slider 12.
FIG. 2 shows a suspension arm 20 mounted to the top surface of slider 12 and a transducer 22 mounted to the top surface of wing 18. The suspension arm 20 positions glide head 10 over the disk as it rotates while glide head 10 tests the disk for defects. Transducer 22 is conventionally a piezoelectric transducer and is used to convert the mechanical energy that is created by glide head 10 physically contacting an asperity on the surface of the disk to an electric signal. Other types of transducers may also be used.
Glide head 10 is called a 50% glide head because slider 12 is approximately 50% the size of an original 100% glide head. As is well understood in the art, however, with wing 18 serving as an extension to slider 12, the overall width of glide head 10, including slider 12 and wing 18, is approximately the same as an original 100%. A 50% glide head has, e.g., a length L10 of approximately 0.080 inches, a total width WTOT10 of approximately 0.10 inches (with slider 12 width W12 approximately 0.060 inches, and wing width W18 approximately 0.040 inches), and a height H10 of approximately 0.024 inches.
FIG. 3 shows a top view of suspension arm 20 mounted to the top surface of glide head 10. It should be understood that while FIG. 3 shows a top view of suspension arm 20, glide head 10 is shown in its entirety, i.e., slider 12 is shown unobscured, for the sake of clarity. As can be seen in FIG. 3, the width of slider 12 is approximately the same as the width W20 of suspension arm 20, which is approximately 0.070 inches. With larger glide heads, i.e., 100% and 70% glide heads, the slider portion was large enough that the suspension arm 20 did not cover the entire top surface of the slider. Consequently, the transducer could be mounted to the top surface of the glide head slider without interfering with the suspension arm. However, as shown in FIG. 3, with a 50% glide head, the slider 12 is approximately the same size as the suspension arm 20, leaving no room to mount a transducer. Thus, wing 18 is used as an extension to slider 12 and extends the top surface of glide head out from under the suspension arm 20. Consequently, transducer 22 can be mounted on wing 18 without interfering with suspension arm 20.
The next reduction in size for glide heads will be 30%, i.e., the glide head slider is 30% of the 100% slider. FIG. 4 is a perspective view of a conventional 30% slider 30. Slider 30 includes two rails 32 and 34 with tapered leading ends 33 and 35, respectively. A conventional slider 30 has dimensions that are approximately 30% of a 100% slider, e.g., a length L30 of approximately 0.048 inches, a width W30 of approximately 0.038 inches, and a height H30 of approximately 0.010 inches.
Because the size of suspension arms have not had a decrease in size corresponding to the decrease in the size of sliders, 30% slider 30 will be much smaller than a suspension arm, leaving no room for a transducer to be mounted to slider 30. Thus, like the 50% glide head 10, shown in FIG. 3, a transducer cannot be mounted to the top surface of a 30% glide head without the presence of a wing that extends beyond the suspension arm.
FIG. 5 shows a top view of suspension arm 20 mounted to the top surface of a 30% glide head 40, which includes slider 30 and a wing 36 that extends from slider 30. As shown in FIG. 5, wing 36 extends beyond suspension arm 20 by an amount sufficient for transducer 22 to be mounted to wing 36 without interfering with suspension arm 20. FIG. 5, similar to FIG. 3, shows slider 30 in its entirety, i.e., unobscured by the suspension arm 20, for the sake of clarity. Because wing 36 is required to extend beyond suspension arm 20 and to provide a large enough surface to mount transducer 22, the wing 36 of glide head 40 is much larger than slider 30. Consequently, wing 36 will alter the flight characteristics of glide head 40. For example, the mass of wing 36 will provide torque on slider 30 causing slider 30 to roll during flight. Further, because wing 36 has a large surface area, wing 36 may alter the lift characteristics of the glide head and may cause undesirable vibrations. Thus, a conventional wing configuration with a small, e.g., thirty percent, glide head slider has certain disadvantages.
Another configuration that could be used with a 30% slider is to mount the transducer on suspension arm 20, rather than on the slider itself. For example, the transducer may be mounted at the end 21 of suspension arm 20. With the transducer mounted to the end of the suspension arm, there is no need for a wing to extend the top surface of slider 30. Unfortunately, a transducer mounted on suspension arm 20 will not directly receive vibrations from slider 30 when slider 30 contacts defects on the surface of a disk, but rather must receive the vibrations through the junction of slider 30 and suspension arm 20. Unfortunately, with the transducer separated from the slider, only low frequency vibrations will be detected by the transducer. Consequently, such a configuration results in the loss of higher frequencies, which sometimes provide the most valuable information.
Thus, what is needed is a glide head to which a transducer can be directly mounted without interfering with the suspension arm. This is particularly desirable where the glide head is smaller in size than the width of the suspension arm.
In accordance with an embodiment of the present invention, a glide head that is used for testing disk substrates for defects includes a transducer mounted on a side surface, e.g., the leading side, of the glide head slider. With the transducer mounted on a side surface of the glide head slider, as opposed to being conventionally mounted on a top surface or on a wing of the glide head, a suspension arm may be mounted to the top surface of a small glide head slider, e.g., a thirty percent slider, without interference from the transducer. The side surface of the glide head slider may include a notch or a groove into which at least a portion of the transducer is inserted to securely mount the transducer to the glide head slider. The notch may be positioned approximately midway between the top surface and the bottom surface of the glide head slider and may extend across the entire side surface, i.e., from one side to the opposing side of the glide head slider. The height of the glide head slider may be increased to accommodate the presence of the transducer without permitting the transducer to extend above or below the top or bottom surfaces of the glide head slider. With the increased height of the glide head slider, the glide head slider may have a height to length ratio of greater than forty percent. For example, for a 30% glide head slider, the height to length ratio may be seventy percent.
The transducer that is mounted to the side surface of the glide head slider may be, e.g., a piezoelectric transducer that includes a first collector and a second collector and piezoelectric material disposed between. The piezoelectric transducer may be mounted with one of the collectors against the glide head slider body, which improves the operation of the transducer. The transducer may be laterally mounted, i.e., with an axis between the collectors horizontally oriented, which prevents wires extending from the collectors from unintentionally extending above or below the top or bottom surfaces of the glide head slider. Thus, the suspension arm may be mounted to the top surface of the glide head slider and the transducer does not contact or interfere with the suspension arm.
The glide head may be manufactured by providing a substrate that is cut into slices, each slice having a top surface, a bottom surface, and four sides. A plurality of grooves may be produced in the top surface of the substrate prior to cutting out slices. Once the slice is cut out, the groove is located on one of the sides of the slice. Rails are produced on the bottom surface of the slice, e.g., after the top surface is mounted to a transfer tool to hold the slice. Individual glide head sliders are then cut out of the slice and a transducer is mounted to one of the sides, e.g., the leading side of the glide head slider. The transducer is mounted to the side of the glide head slider by inserting at least a portion of the transducer into the groove. A suspension arm can then be mounted to the top surface of the glide head slider without interference from the transducer.